US20060195191A1 - Modular disc device - Google Patents

Abstract

The disclosure generally relates to a modular disc that is insertable by sections into a disc space located between vertebral bodies. The primary segments of the modular disc are one or more middle members engageable with first and second side members. The first and second side members are successively inserted into and positioned in the disc space one at a time. The middle member is then slidably engaged on rails extending from the respective first and second side members. Eventually, the middle member is moved along the guides and positioned between the respective first and second side members and the guides or rails are detached. Optionally, a cushioning and/or biasing member may be located between upper and lower portions of the side members and/or middle member.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS
• This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Nos. 60/642,256 filed Jan. 8, 2005, 60/622,097 filed Oct. 25, 2004, 60/687,500 filed Jun. 3, 2005, 60/687,185 filed Jun. 3, 2005, 60/687,498 filed Jun. 3, 2005, and 60/687,499 filed Jun. 3, 2005, where these provisional applications are also incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates generally to a modular disc that is insertable between vertebral bodies and functions as an artificial replacement intervertebral disc for a spine.
• 2. Description of the Related Art
• The intervertebral discs are the cushions that act as shock absorbers between each of the vertebra in a person's spine. There is one disc between each pair of the vertebrae. Each disc has a strong outer ring of fibers called the annulus and a soft, jelly-like center called the nucleus pulposus. The annulus is the outermost and strongest portion of the disc. The annulus is also a ligament and functions to connect the vertebrae together. The nucleus of the disc serves as the main shock absorber.
• Intervertebral discs become more rigid with age, which means that the elasticity of the disc decreases and makes it more vulnerable to injury. One type of injury that may occur to an intervertebral disc is a herniated disc or rupture of the intervertebral disc. A herniated disc occurs when the annulus becomes damaged and allows the soft inner material of the nucleus pulposus to rupture out of a disc space defined by the annulus. If the annulus tears near the spinal canal, the nucleus pulposus material can push into the spinal canal. When a herniated disc bulges out from between the vertebral bodies and from the annulus, the spinal nerves and spinal cord can become pinched and/or compressed.
• Artificial disc replacement is designed to restore the normal disc height by replacing at least a portion of a damaged intervertebral disc with an artificial disc implant. There are several types of artificial discs available including those fabricated from combinations of metal, polyethylene, polyurethane, and other biomaterials. Some of these artificial discs are referred to by the trade names of FlexiCore®, ProDisc®, and Maverick™.
• Although artificial intervertebral discs have been used internationally for over a decade, only the Charité™ artificial disc has received the approval of the Food and Drug Administration (FDA). The Charité™ artificial disc is a three-piece articulating medical device with a sliding core sandwiched between two metal endplates. The sliding core is made from plastic and the endplates are made from a cobalt chromium alloy. The endplates support the core and have small teeth or barbs that secure them to the vertebrae above and below the disc space. The sliding core fits between the endplates.
BRIEF SUMMARY OF THE INVENTION
• The embodiments described herein are generally related to a modular disc that can be used as a replacement for a natural intervertebral disc. The modular disc is insertable into a disc space of a patient in segments. The modular disc comprises a middle member disposed between and engageable with respective side members. The side members are inserted into and positioned in the disc space one at a time. The middle member is slidably engaged and disposed between the respective side members. Optionally, a cushioning and/or biasing member may be located between upper and lower portions of the side members and/or middle member.
• In one aspect, a modular disc includes a middle member having engagement portions; and first and second side members having complementary engagement portions, the middle member disposed between the first and second side members, wherein the middle member is slidably engageable with the first and second side members.
• In another aspect, a modular disc includes a middle member having an engagement portion; and a first side member having a first complementary engagement portion comprising a first portion and a second portion, the first portion positioned proximate the first side member, the second portion extending radially from an outer circumference of the first side member, wherein the engagement portion of the middle member is slidably engageable with the first and second portions of the complementary engagement portion of the first side member.
• In yet another aspect, a method of inserting a spinal disc between vertebral bodies includes inserting a first side member into a first portion of a disc space located between the vertebral bodies, the first side member having an engagement member with a first engagement portion and a second engagement portion, the first engagement portion coupled to the first side member and locatable within the disc space, the second engagement portion extending from the first engagement portion and protrudable from the disc space in a first direction; inserting a second side member into a second portion of the disc space, the second side member having an engagement member with a first engagement portion and a second engagement portion, the first engagement portion coupled to the second side member and locatable within the disc space, the second engagement portion extending from the first engagement portion and protrudable from the disc space in substantially the first direction; slidably engaging middle members with the second engagement portions of the first and second side members; sliding the middle members along the second engagement portions of the first and second side members; sliding the middle members along the first engagement portions of the first and second side members until the middle members are located within the disc space; and detaching the second engagement portions of the first and second side members.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
• In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility.
• FIG. 1 is an isometric view of a modular disc having a middle member disposed between side members, according to one illustrated embodiment.
• FIG. 2 is a top plan view of the modular disc ofFIG. 1 after extendable engagement portions of the side members have been removed.
• FIG. 3 is a cross-sectional view of the modular disc ofFIG. 1 taken along line3-3 ofFIG. 2.
• FIG. 4 is a detailed view of an engagement between one of the middle members and one of the side members of the modular disc ofFIG. 1.
• FIG. 5 is a top plan view of the modular disc ofFIG. 1 before the extendable engagement portions of the side members have been removed.
• FIG. 6 is a cross-sectional view of another modular disc illustrating an alternative engagement of the middle members to the side members.
• FIG. 7 is an isometric view of a modular disc having a biasing member disposed between side members, according to one illustrated embodiment.
• FIG. 8 is a front side elevational view of the modular disc ofFIG. 7.
• FIG. 9 is a right side elevational view of the modular disc ofFIG. 7.
• FIG. 10 is a bottom, left isometric view of the modular disc ofFIG. 7 before extendable engagement portions of the side members have been removed.
• FIG. 11 is a side elevational view of a portion of a spine showing a number of vertebral bodies separated by intervertebral discs.
• FIG. 12 is a schematic view of a surgical site showing an annulus of an intervertebral disc with a disc space and an access region.
• FIG. 13 is a schematic view of first side members of a modular disc being inserted in through the access region and into the disc space of the annulus.
• FIG. 14 is a schematic view of first side members and second side members positioned in the disc space of the annulus.
• FIG. 15 is a schematic view of middle members of a modular disc being slidably engaged with rail guides extending from the first and second side members of the modular disc.
• FIG. 16 is a schematic view of an assembled modular disc positioned within the disc space of the annulus and having rail guides extending out of the disc space through the access region of the annulus.
• FIG. 17 is a schematic view of an assembled modular disc positioned within the disc space of the annulus and with the rail guides ofFIG. 16 detached from the modular disc.
DETAILED DESCRIPTION OF THE INVENTION
• In one embodiment, a modular disc can be used as a replacement for a natural intervertebral disc. The modular disc is insertable into a disc space of a patient in segments or sections. The primary segment of the modular disc is a middle member, which may comprise one or two pieces, and which is engageable with first and second side members. The first and second side members are successively inserted into and positioned in the disc space one at a time. The middle member is then slidably engaged with guides or rails extending from the respective first and second side members. The middle member is moved along the guides and positioned between the respective first and second side members and the extending guides or rails are removed. Optionally, a cushioning and/or biasing member may be located between upper and lower portions of the side members and/or between the first and second pieces of the middle member.
• FIGS. 1 and 2 show amodular disc100 havingmiddle member102,first side members104, andsecond side members106, according to one illustrated embodiment. In addition, themodular disc100 may optionally include a cushioning, damping, biasing, and/or otherwiseresilient member108 disposed between upper and lower portions of theside members104,106. In one embodiment the cushioningmember108 is an elastomeric material. In another embodiment, the cushioningmember108 is a biasing member, which will be described in greater detail below. The upper and lower surfaces of themodular disc100 may be hardened or coated to achieve an improved bearing surface with the vertebral bodies.
• FIGS. 3 and 4 show themodular disc100 with a two-piecemiddle member102 engageably keyed to thefirst side members104 and thesecond side members106. InFIG. 4,engagement portions110 of themiddle member102 comprise a recessed or keyedslot110. Theengagement portions110 of the middle member are sized to closely, yet slidably, receivecomplementary engagement portions112 of thefirst side members104.
• FIG. 4 shows a detailed view of oneengagement portion110 of themiddle member102 coupled to onecomplementary engagement portion112 of onefirst side member104. In the illustrated embodiment, thecomplementary engagement portion110 of the first side member is a protuberance or key112 located proximate to and extending adjacently from afirst surface114 of thefirst side member104. Theprotuberance112 includes anarrow base116 proximate thefirst surface114. Theprotuberance112 extends or flares out to awide portion118 as it extends from thefirst surface114 to form an interlockingkey112 that is engageable with theengagement portion110 of themiddle member102. In one embodiment, theprotuberance112 and theengagement portion110 operate as dovetail portions for adjoining the components together. In an alternate embodiment, theside members104,106 may include slots and themiddle member102 may include protuberances.
• FIG. 5 shows thefirst side member104, which is representative of the other side members, where thecomplementary engagement portion112 includes afirst portion120 and asecond portion122. Thefirst portion120 is positioned adjacent and proximate to thefirst side member104. Thesecond portion122 extends radially from anouter circumference124 of thefirst side member104 in afirst direction126. In addition, thecomplementary engagement portion112 may include a reducedshear strength region128 to allow thesecond portion122 to be easily separated from thefirst portion120 after thefirst side member104 has been placed in a disc space of a patient. The installation of themodular disc100 and the purpose of having both thefirst portion120 and thesecond portion122 of thecomplementary engagement portion112 is described in greater detail below.
• FIG. 6 shows amodular disc200 having a two-piecemiddle member202,first side members204,second side members206, and a cushioningmember208. Themiddle member202 includesengagement portions210. Theside members204,206 includecomplementary engagement portions212, which are formed asbulbous protuberances212 extending from afirst surface214.
• FIG. 7 shows anothermodular disc300 comprising a two-piecemiddle member302,first side members304,second side members306, and biasingmembers308. The biasingmembers308 are disposed between and coupled to the upper and lower portions of the respective first andsecond side members304,306. The biasingmembers308 can be springs, damping members, or some combination of a spring/damper device. In one embodiment, the biasingmembers308 comprise leaf springs, Belleville springs, or coil springs. The biasingmembers308 are capable of compressing, but may also extend, when reacting to static and dynamic loading of the spine. This loading may cause the vertebral bodies to be forced closer together (i.e., biasing is urged into compression) or pulled further apart (i.e., biasing is urged into extension) from one another. The biasingmembers308 react to such loading and then return the vertebral bodies back to a neutral or a rest position when the loading is complete. In addition, the biasingmembers308 couple the upper and lower portions of the side members together, which increases stability of themodular disc300 while under load.
• Alternatively, the biasingmembers308 may comprise at least one spacer insertable between the upper andlower side members304,306 and/or between the upper and lowermiddle members302. The at least one spacer may be an articulating spacer that complementarily contacts at least some portion of the inner surfaces of the middle and/or side members. Accordingly, the articulating spacer would permit the upper and lower portions of themodular disc300 to rotate independently of one another.
• FIGS. 8 and 9 show respective side views of themodular disc300.FIG. 8 shows that themiddle members302 are engaged with theside members304,306 in a manner similar to that described in the previous embodiment.FIG. 9 shows the biasingmembers308 comprising a curved leaf spring coupled to upper and lower portions of the respective first andsecond side members304,306. Additionally or alternatively, a biasing member (not shown) may be disposed between and coupled to the upper and lowermiddle members302.
• FIG. 10 shows thefirst side members304 and a biasingmember308 of themodular disc300 coupled together. Thefirst side members304 each include acomplementary engagement portion312, which is in a pre-installed state. Thecomplementary engagement portions312 include afirst portion320 and asecond portion322. Thefirst portion320 is positioned adjacent and proximate to the respectivefirst side member304. Thesecond portion322 extends radially from an outer circumference324 of the respectivefirst side member304 in afirst direction326.
• Installation of a Modular Disc
• FIG. 11 shows a portion of aspine400 havingvertebral bodies402 andintervertebral discs404, which act as cushions between thebodies402. Each disc includes a tough, fibrous outer layer called an annulus and a softer center portion called a nucleus. During a surgical procedure to insert a modular disc, the nucleus is removed, but the annulus is kept in place.
• FIG. 12 shows a spinalsurgical site500 where anannulus502 has been prepared to receive the modular disc. Theannulus502 includes adisc space504 and anaccess region506 to receive the modular disc.
• FIG. 13 showsfirst side members508 having radially extendingguides510 being inserted through theaccess region506. Thefirst side members508 are positioned in afirst region512 of thedisc space504. Second side members514 (FIG. 14) are inserted and positioned in asecond region516 of thedisc space504.
• FIG. 14 shows thefirst side members508 and thesecond side members514 positioned in thedisc space502. Theradially extending guides510 of thefirst side members508 and radially extendingguides518 of thesecond side members514 protrude from theaccess region506 of theannulus502 and may be adjusted to receive middle member520 (FIG. 15).
• FIG. 15 shows themiddle members520 slidably engaging theradially extending guides510,518 of therespective side members508,514. Themiddle member520 is pushed onto theguides510,518 toward theaccess region506 of theannulus502 as indicated by thearrow522.
• FIG. 16 shows themiddle member520 coupled with theside members508,514 after themiddle member520 has been slid down theguides510,518 and into thedisc space504 of theannulus502. Theguides510,518 remain attached and protruding from theside members508,514 and protruding out through theaccess region506 of theannulus502.
• FIG. 17 shows the assembled and installed modular disc524 after theguides510,518 have been detached from therespective side members508,514. In one embodiment, theguides510,518 are snapped, broken, or clipped off near the perimeter of the modular disc524.
• The modular discs described herein are installed in sections, for example the first side member, the second member, and then the middle member. This sectional installation approach may advantageously permit an opening to the surgical site to be smaller because the surgeon does not need to separate and/or remove a lot of tissue to maneuver the modular disc section through the body to the surgical site. This may reduce the amount of trauma to the tissue near the surgical site, which in turn may allow a faster recovery time for the patient. One other aspect of having a smaller surgical opening is that the modular disc may be inserted using a posterior (i.e., through a patient's back) or lateral (i.e., through a patient's side) approach. This other aspect provides an advantage over other spinal replacement discs because those discs are sized to be installed using an anterior approach, which results in a larger surgical opening through a patient's stomach. It is generally understood the access to the spine via the posterior or lateral approach is more limited than via the anterior approach.
• In addition, the components of the modular disc are coupled together during assembly/installation of the disc, thus these components operate to provide a stable structure with redundant and/or backup load paths (e.g., multiple biasing members).
• The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Although specific embodiments of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the invention, as will be recognized by those skilled in the relevant art. The teachings provided herein of the invention can be applied to various disc devices, not necessarily the exemplary disc devices generally described above.
• The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, to include U.S. patent application Ser. No. 11/260,880 filed Oct. 25, 2005; U.S. Provisional Patent Application Nos. 60/642,256 filed Jan. 8, 2005; 60/622,097 filed Oct. 25, 2004;, 60/687,500 filed Jun. 3, 2005;, 60/687,185 filed Jun. 3, 2005;, 60/687,498 filed Jun. 3, 2005;, and 60/687,499 filed Jun. 3, 2005; are incorporated herein by reference, in their entireties. Aspects of the invention can be modified, if necessary, to employ aspects of other disc devices and concepts of the various patents, applications, and publications to provide yet further embodiments of the invention.
• These and other changes can be made to the invention in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all spinal disc devices that operate in accordance with the claims. Accordingly, the invention is not limited by the disclosure, but instead its scope is to be determined entirely by the following claims.

Claims (36)

1. A modular disc comprising:

a middle member having engagement portions; and

first and second side members having complementary engagement portions, the middle member disposed between the first and second side members, wherein the middle member is slidably engageable with the first and second side members.

2. The modular disc ofclaim 1 wherein the engagement portions of the middle member comprise recessed slots.

3. The modular disc ofclaim 1 wherein the engagement portions of the middle member comprise keyed slots.

4. The modular disc ofclaim 1 wherein the engagement portions of the middle member comprise dovetail portions extending laterally therefrom.

5. The modular disc ofclaim 1 wherein the complementary engagement portions of the first and second side members comprise recessed slots.

6. The modular disc ofclaim 1 wherein the complementary engagement portions of the first and second side members comprise keyed slots.

7. The modular disc ofclaim 1 wherein the complementary engagement portions of the first and second side members comprise dovetail portions extending laterally therefrom.

8. The modular disc ofclaim 1 wherein the complementary engagement portions of the first and second side members comprise guide tracks extending therefrom.

9. The modular disc ofclaim 1 wherein the first and second side members include upper and lower portions.

10. The modular disc ofclaim 1, further comprising:

an intermediate member disposed between the upper and lower portions of the first and second side members.

11. The modular disc ofclaim 10 wherein the intermediate member is a biasing member.

12. The modular disc ofclaim 11 wherein the biasing member is a spring.

13. The modular disc ofclaim 10 wherein the intermediate member is a damping member.

14. The modular disc ofclaim 13 wherein the damping member is an elastomeric member.

15. The modular disc ofclaim 10 wherein the intermediate member is a spacer.

16. The modular disc ofclaim 1, further comprising:

an intermediate member disposed between the upper and lower portions of the middle member.

17. The modular disc ofclaim 1 wherein the middle member is a two-piece middle member.

18. A modular disc comprising:

a middle member having an engagement portion; and

a first side member having a first complementary engagement portion comprising a first portion and a second portion, the first portion positioned proximate the first side member, the second portion extending radially from an outer circumference of the first side member, wherein the engagement portion of the middle member is slidably engageable with the first and second portions of the complementary engagement portion of the first side member.

19. The modular disc ofclaim 18 wherein the engagement portion of the middle member comprises a recessed slot.

20. The disc ofclaim 18 wherein the engagement portion of the middle member comprises a keyed slot.

21. The modular disc ofclaim 18 wherein the engagement portion of the middle member comprises a dovetail portion.

22. The modular disc ofclaim 18 wherein the complementary engagement portion of the first side member comprises a recessed slot.

23. The modular disc ofclaim 18 wherein the complementary engagement portion of the first side member comprises a keyed slot.

24. The modular disc ofclaim 18 wherein the complementary engagement portion of the first side members comprises a dovetail extension.

25. The modular disc ofclaim 18 wherein the complementary engagement portion of the first side member comprise a guide track.

26. The modular disc ofclaim 18, further comprising:

an intermediate member positioned adjacent to the first side member.

27. The modular disc ofclaim 26 wherein the intermediate member is a biasing member.

28. The modular disc ofclaim 27 wherein the biasing member is a spring.

29. The modular disc ofclaim 26 wherein the intermediate member is a damping member.

30. The modular disc ofclaim 29 wherein the damping member is an elastomeric member.

31. The modular disc ofclaim 26 wherein the intermediate member is a spacer.

32. The modular disc ofclaim 18 wherein the complementary engagement portion includes a decreased strength region located proximate the outer circumference of the first side member.

33. A method of inserting a spinal disc between vertebral bodies, the method comprising:

inserting a first side member into a first portion of a disc space located between the vertebral bodies, the first side member having an engagement member with a first engagement portion and a second engagement portion, the first engagement portion coupled to the first side member and locatable within the disc space, the second engagement portion extending from the first engagement portion and protrudable from the disc space in a first direction;

inserting a second side member into a second portion of the disc space, the second side member having an engagement member with a first engagement portion and a second engagement portion, the first engagement portion coupled to the second side member and locatable within the disc space, the second engagement portion extending from the first engagement portion and protrudable from the disc space in substantially the first direction;

slidably engaging a middle member with the second engagement portions of the first and second side members;

sliding the middle member along the second engagement portions of the first and second side members;

sliding the middle member along the first engagement portions of the first and second side members until the middle member is located within the disc space; and

detaching the second engagement portions of the first and second side members.

34. The method ofclaim 33 wherein detaching the second engagement portions of the first and second side members includes breaking off the second engagement portions along a reduced strength region proximate the first engagement portions.

35. The method ofclaim 33 wherein inserting the spinal disc between vertebral bodies includes inserting the spinal disc through a posterior surgical opening.

36. The method ofclaim 33 wherein inserting the spinal disc between vertebral bodies includes inserting the spinal disc through a lateral surgical opening.

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